Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
  Case Tag  
Price  
Sales  
Tax %  
Raw Total  
Incl. Sales Tax  
Rounded  
to Penny  
Rounded  
to Nickel  
Rounded  
to Dime  
  Purchase #1 $35.76   3.361%   $36.9619   $36.96   $36.95   $37.00  
  Purchase #2 $235.49   6.768%   $251.428   $251.43   $251.45   $251.40  
  Purchase #3 $38.73   7.621%   $41.6816   $41.68   $41.70   $41.70  
  Purchase #4 $240.59   5.797%   $254.537   $254.54   $254.55   $254.50  
  Purchase #5 $137.84   10.215%   $151.9204   $151.92   $151.90   $151.90  
  Purchase #6 $201.45   8.119%   $217.8057   $217.81   $217.80   $217.80  
  Purchase #7 $193.87   9.105%   $211.5219   $211.52   $211.50   $211.50  
  7 purchase totals = $1,083.73       $1,165.8565   $1,165.86   $1,165.85   $1,165.80